Field of the Invention
The present invention relates to an electronic configuration with electrical contacts, at least on a first surface of the electronic configuration, which enable the electronic configuration to be electrically bonded. The electronic configuration may in this case take the form of an electronic component or a component carrier, for example.
Electrical bonding of these configurations, for example, by means of solder balls, contact pins, or directly soldered connections between the electronic configuration and a further configuration (for example between a component and a carrier on which the component is to be mounted) is problematic to the extent that thermal loading may cause different linear expansions of the electronic configurations. This results in mechanical stresses at the soldered connections between the electronic configurations (that is to say, for example, between the component carrier and the electronic component). Such stresses may also occur, however, as a result of other mechanical loads on the configurations. One consequence of these stresses is the risk of damage or destruction to the soldered connections between the electronic configurations.
It is known from the prior art, as disclosed by U.S. Pat. No. 5,685,885, to arrange electrical contacts on a flexible layer. However, this layer has proven to be insufficiently elastic to optimally absorb the mechanical stresses that occur. In addition, the production of components with the layer disclosed there is relatively complicated.
It is accordingly an object of the invention to provide an electronic configuration and a method for producing the electronic configuration which overcome the above-mentioned disadvantages of the prior art apparatus and methods of this general type.
In particular, it is an object of the invention to provide an electronic configuration and a method for producing the electronic configuration in which greater insensitivity to mechanical stresses is obtained in the region of the electrical contacts.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for producing an electronic configuration having a first surface with at least one electrical contact for bonding. The method includes steps of: providing an electronic configuration having a first surface; configuring at least one flexible elevation made of an insulating material on the first surface; providing the flexible elevation with at least one recess; at least partially covering a surface of the flexible elevation with an electrically conductive material to form an electrical contact; applying an insulating layer at least partially to the first surface; forming a structural feature in a region of the insulating layer; forming the structural feature as a feature selected from the group consisting of a depression formed in the region of the insulating layer and a roughened surface formed in the region of the insulating layer; providing the insulating layer with a metallization at least in the region of the structural feature; and forming a recess selected from the group consisting of a first recess running perpendicularly in relation to the first surface and a second recess running parallel in relation to the first surface. When selecting the first recess as the recess, the flexible elevation is configured over the structural feature. When selecting the second recess as the recess, the flexible elevation is configured directly alongside the structural feature. The method also includes steps of: performing the step of forming the recess by directing laser light towards the structural feature such that the structural feature performs an operation selected from the group consisting of focusing the laser light and scattering the laser light; and applying an electrically conductive material at least partially to the surface of the flexible elevation.
At least one flexible elevation made of an insulating material is provided on the first surface of the electronic configuration on which the electrical contacts of the configuration are arranged. At least one electrical contact is arranged on the flexible elevation and is in the form of an electrically conductive material that at least partially covers the surface of the flexible elevation. This consequently elastically attaches the electrical contacts on the electronic component, so that, under thermal or mechanical loading of the component, the corresponding stresses are absorbed by the flexible elevation. This is performed much better in the case of an elevation, as opposed to the prior art straight-extending layer, since the elevation has a greater freedom of movement and can therefore compensate for greater tolerances. The flexible elevation has a recess enabling the flexibility of the elevation to be further enhanced.
In principle, the entire flexible elevation may also be produced from a flexible and electrically conductive material, so that the conducting connection is not established by a separate conduction path of a different material, but by the flexible material itself. However, very specific materials are necessary to achieve this, restricting the selection of flexible materials and their composition. What is more, such materials are generally more resistive than a purely conductive material, which forms a conductive path. In the preferred solution, in which the electrically conductive material covers the surface of the flexible elevation, a separate optimization of the flexible characteristics and of the conduction characteristics of the elevation is consequently possible.
This configuration has special significance in the case of electronic components which have a size that may, for example, correspond largely to the size of the electronic circuit, or of the circuit chip of the component, such as chip-size components, for example. Particularly in this specific case, apart from the electronic circuit or the circuit chip, there are virtually no other housing elements that could absorb the stresses on the electronic component. In the case of such components, there is a particularly high risk that the electrical contacts will be damaged or destroyed. Particularly in such a case, the occurrence of excessive mechanical stresses can be avoided, and consequently the operational reliability of the component ensured, by a flexible elevation such as that proposed according to the invention. However, the inventive teaching may also be advantageously used in the case of any other electronic configurations.
The electrical contacts of the electronic component are consequently arranged on a flexible elevation that compensates for the mechanical stresses that occur. To establish a conducting connection to an electrical contact on an elevation, a conductive path can be arranged on the outer surface of the flexible elevation, that is to say outside the recess. As an alternative to the conductive path on the outer surface of the flexible elevation, a conductive path may also be arranged in the recess of the flexible elevation. The conducting connection is consequently routed over the inner surface of the flexible elevation, that is to say, over the surface formed by the recess.
An electronic circuit, which is connected in a conducting manner to the electronic contacts, may then be provided in the electronic configuration. The electronic circuit may, for example, directly adjoin the flexible elevation, but additional conductor runs may also be arranged between the flexible elevation and the electronic circuit, so that the flexible elevation can be arranged at a distance from the electronic circuit.
If further conductor runs are provided, for example, between an electronic circuit and the flexible elevation, they may be arranged on an insulating layer that at least partially covers the first surface of the electronic component, with the insulating layer adjoining the flexible elevation. This has the advantage that the conductor runs can be structured by indirect structuring, to be specific, by structuring the insulating layer.
The recess that is provided in the flexible elevation may be formed in various ways. It may be provided that the recess extends parallel in relation to the first surface into the flexible elevation. In particular, the recess may, in this case, be formed by a notching or an indentation formed in the surface of the flexible elevation in which the indentation runs parallel in relation to the first surface. However, the recess may also have, for example, the form of a channel or of a tube running through the flexible elevation.
It may alternatively be provided that the recess extends into the flexible elevation perpendicularly in relation to the first surface. The recess may in this case be formed, for example, by a trough-shaped or trench-shaped indentation or notch formed in the surface of the flexible elevation and configured perpendicularly in relation to the first surface. The recess may also be, for example, as a dish-shaped hollowing of the flexible elevation formed perpendicularly in relation to the first surface.
A corresponding shaping of the recess in the flexible elevation can still further improve the flexibility of the flexible elevation. This is achieved by the reduction in the cross-sectional area of the flexible elevation, which is brought about by the recess.
On the other hand, however, the shaping of the flexible elevations may be made to match one another in such a way that two flexible elevations respectively interact with each other, and can in this way form an electrical contact. For example, an elevation whose recess extends parallel in relation to the first surface may in each case interact with an elevation whose recess extends perpendicularly in relation to the first surface, in accordance with a press-stud principle, with the first elevation engaging in the recess of the second elevation. In this way, for example, electrical contacts can be formed within electronic modules, so that a conducting connection can be established from a first electronic configuration to a second electronic configuration. The first configuration may in this case be in the form of an electronic component, and the second configuration can be in the form of a component carrier or else a further electronic component, for example.
A method for producing an electronic configuration such as that described above is presented below. In a first step, an insulating layer is applied to the first surface, so that the insulating layer at least partially covers the first surface. Subsequently, a depression is structured into the insulating layer, or the surface of the insulating layer is roughened at least in the region on or alongside which the flexible elevation is to be placed. Then, the insulating layer is provided with a metallization, at least in the region of the at least one depression. Finally, the flexible elevation is arranged over the at least one depression or directly alongside the at least one depression and the recess is formed using a laser.
This method proves to be particularly advantageous, because if only laser structuring were performed, it might be too inaccurate for creating the recesses desired, or could only be performed with relatively complicated means. Rather, the fact is exploited that the depression previously formed depression in the insulating layer and its subsequent metallization create a focusing mirror on the first surface. An appropriate configuration of the depression and of the flexible elevation, additionally focuses the laser radiation acting on the flexible elevation, so that the formation of the recess in the desired form is achieved or is possibly assisted.
If, for example, the flexible elevation is arranged directly over the depression, laser irradiation directed perpendicular to the first surface does not produce a funnel-shaped hollowing, but rather produces a trough-shaped or dish-shaped hollowing of the flexible elevation. If, on the other hand, the flexible elevation is arranged directly alongside one or more depressions, with laser irradiation directed perpendicular in relation to the first surface, the laser radiation is focused on the side walls of the flexible elevation so that an indentation or notching is formed parallel in relation to the first surface.
An analogous situation applies if, instead of a depression, a rough surface is created on the insulating layer and then is metallized. This produces a scattering reflection mirror, which scatters back the impinging light in a wide variety of different spatial directions, and consequently likewise structures the recess in directions that deviate from the (ideally perpendicular) direction of incidence of the laser radiation. The application of the metallization does not represent an additional method step, since the metallization can also be used at the same time for forming conduction paths or conductor runs on the electronic configuration.
The insulating layer is preferably applied to the first surface using a pressure process, which can be carried out easily and at low cost and nevertheless with the required accuracy. Similarly, the flexible elevation can also be applied by such a pressure process. Like the formation of the recess, the formation of the depression or depressions in the insulating layer may likewise be performed using a laser.
The conductive material for producing the conductor runs or the conduction paths and the electrical contacts may be applied to the flexible elevation or to the insulating layer by customary methods, such as, for example, sputter metallization or chemical metallization. Specific methods to achieve this are described in International Publication WO 98/55 669 and in International Publication WO 99/05 895, with initial nucleation in an insulating layer and subsequent metallization of these regions. As an alternative to these prior-art methods, the surface may be roughened by laser treating the surface of the flexible elevation, and possibly also by laser treating the flexible layer, or by some other suitable method that offers better adhesion for the conductive material of the metallization to be applied later. It may also be provided in this case that, before applying the metallization and after roughening the surface, metal nuclei or other suitable nuclei, which may consist of any suitable material, for example palladium, are applied to the rough surface.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an electronic configuration with flexible bonding pads, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.